Prostate cancer is the most common non-skin cancer in American men, resulting in over 30,000 deaths annually in this country. A significant proportion with apparently localized disease still fail after either radiation can be improved in intermediate-to-higher risk prostate cancer patients by delivering higher doses of radiation therapy (IMRT) can deliver these higher doses with acceptable complication rates. IMRT, in particular offers the potential for controlling complication rates through highly conformal delivery of radiation while permitting dose escalation where necessary to enhance tumor control. Helical tomotherapy is a form of IMRT that integrates radiotherapy and helical computed tomography. It has the potential for providing exquisitely conformal therapy, image guidance, improved verification of delivered dose and adaptation to altered delivery or tumor size when necessary. These capabilities should help avoid some of the cumbersome and uncertain methods required with conventional 3DCRT or IMRT for verifying target and normal organ location and delivered zone. The aims of the project are specifically to: 1) evaluated in a phase I trial the clinical feasibility of delivering dose-per-fraction escalation to the prostate using helical tomotherapy; 2) evaluate the process of megavoltage CT imaging and adaptive radiotherapy for its ability to improve treatment precision; and 3) as secondary goals, to record local tumor control and biochemical progression-free survival.